Inflammation, microglia, and Alzheimer's disease

Complement receptor 4 mediates the clearance of extracellular tau fibrils by microglia

Tauopathies exhibit a characteristic accumulation of misfolded tau aggregates in the brain. Tau pathology shows disease-specific spatiotemporal propagation through intercellular transmission, which is closely correlated with the progression of clinical manifestations. Therefore, identifying molecular mechanisms that prevent tau propagation is critical for developing therapeutic strategies for tauopathies. The various innate immune receptors, such as complement receptor 3 (CR3) and complement receptor 4 (CR4), have been reported to play a critical role in the clearance of various extracellular toxic molecules by microglia. However, their role in tau clearance has not been studied yet. In the present study, we investigated the role of CR3 and CR4 in regulating extracellular tau clearance. We found that CR4 selectively binds to tau fibrils but not to tau monomers, whereas CR3 does not bind to either of them. Inhibiting CR4, but not CR3, significantly reduces the uptake of tau fibrils by BV2 cells and primary microglia. By contrast, inhibiting CR4 has no effect on the uptake of tau monomers by BV2 cells. Furthermore, inhibiting CR4 suppresses the clearance of extracellular tau fibrils, leading to more seed-competent tau fibrils remaining in the extracellular space relative to control samples. We also provide evidence that the expression of CR4 is upregulated in the brains of human Alzheimer's disease patients and the PS19 mouse model of tauopathy. Taken together, our data strongly support that CR4 is a previously undescribed receptor for the clearance of tau fibrils in microglia and may represent a novel therapeutic target for tauopathy.

The duality of amyloid-β: its role in normal and Alzheimer's disease states

Alzheimer's disease (AD) is a degenerative neurological condition that gradually impairs cognitive abilities, disrupts memory retention, and impedes daily functioning by impacting the cells of the brain. A key characteristic of AD is the accumulation of amyloid-beta (Aβ) plaques, which play pivotal roles in disease progression. These plaques initiate a cascade of events including neuroinflammation, synaptic dysfunction, tau pathology, oxidative stress, impaired protein clearance, mitochondrial dysfunction, and disrupted calcium homeostasis. Aβ accumulation is also closely associated with other hallmark features of AD, underscoring its significance. Aβ is generated through cleavage of the amyloid precursor protein (APP) and plays a dual role depending on its processing pathway. The non-amyloidogenic pathway reduces Aβ production and has neuroprotective and anti-inflammatory effects, whereas the amyloidogenic pathway leads to the production of Aβ peptides, including Aβ40 and Aβ42, which contribute to neurodegeneration and toxic effects in AD. Understanding the multifaceted role of Aβ, particularly in AD, is crucial for developing effective therapeutic strategies that target Aβ metabolism, aggregation, and clearance with the aim of mitigating the detrimental consequences of the disease. This review aims to explore the mechanisms and functions of Aβ under normal and abnormal conditions, particularly in AD, by examining both its beneficial and detrimental effects.

Early Inhibition of Phosphodiesterase 4B (PDE4B) Instills Cognitive Resilience in APPswe/PS1dE9 Mice

Microglia activity can drive excessive synaptic loss during the prodromal phase of Alzheimer's disease (AD) and is associated with lowered cyclic adenosine monophosphate (cAMP) due to cAMP phosphodiesterase 4B (PDE4B). This study aimed to investigate whether long-term inhibition of PDE4B by A33 (3 mg/kg/day) can prevent synapse loss and its associated cognitive decline in APPswe/PS1dE9 mice. This model is characterized by a chimeric mouse/human APP with the Swedish mutation and human PSEN1 lacking exon 9 (dE9), both under the control of the mouse prion protein promoter. The effects on cognitive function of prolonged A33 treatment from 20 days to 4 months of age, was assessed at 7-8 months. PDE4B inhibition significantly improved both the working and spatial memory of APPswe/PSdE9 mice after treatment ended. At the cellular level, in vitro inhibition of PDE4B induced microglial filopodia formation, suggesting that regulation of PDE4B activity can counteract microglia activation. Further research is needed to investigate if this could prevent microglia from adopting their 'disease-associated microglia (DAM)' phenotype in vivo. These findings support the possibility that PDE4B is a potential target in combating AD pathology and that early intervention using A33 may be a promising treatment strategy for AD.

An overview on microglial origin, distribution, and phenotype in Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease that is responsible for about one-third of dementia cases worldwide. It is believed that AD is initiated with the deposition of Ab plaques in the brain. Genetic studies have shown that a high number of AD risk genes are expressed by microglia, the resident macrophages of brain. Common mode of action by microglia cells is neuroinflammation and phagocytosis. Moreover, it has been discovered that inflammatory marker levels are increased in AD patients. Recent studies advocate that neuroinflammation plays a major role in AD progression. Microglia have different activation profiles depending on the region of brain and stimuli. In different activation, profile microglia can generate either pro-inflammatory or anti-inflammatory responses. Microglia defend brain cells from pathogens and respond to injuries; also, microglia can lead to neuronal death along the way. In this review, we will bring the different roles played by microglia and microglia-related genes in the progression of AD.

Melatonin: a ferroptosis inhibitor with potential therapeutic efficacy for the post-COVID-19 trajectory of accelerated brain aging and neurodegeneration

The unprecedented pandemic of COVID-19 swept millions of lives in a short period, yet its menace continues among its survivors in the form of post-COVID syndrome. An exponentially growing number of COVID-19 survivors suffer from cognitive impairment, with compelling evidence of a trajectory of accelerated aging and neurodegeneration. The novel and enigmatic nature of this yet-to-unfold pathology demands extensive research seeking answers for both the molecular underpinnings and potential therapeutic targets. Ferroptosis, an iron-dependent cell death, is a strongly proposed underlying mechanism in post-COVID-19 aging and neurodegeneration discourse. COVID-19 incites neuroinflammation, iron dysregulation, reactive oxygen species (ROS) accumulation, antioxidant system repression, renin-angiotensin system (RAS) disruption, and clock gene alteration. These events pave the way for ferroptosis, which shows its signature in COVID-19, premature aging, and neurodegenerative disorders. In the search for a treatment, melatonin shines as a promising ferroptosis inhibitor with its repeatedly reported safety and tolerability. According to various studies, melatonin has proven efficacy in attenuating the severity of certain COVID-19 manifestations, validating its reputation as an anti-viral compound. Melatonin has well-documented anti-aging properties and combating neurodegenerative-related pathologies. Melatonin can block the leading events of ferroptosis since it is an efficient anti-inflammatory, iron chelator, antioxidant, angiotensin II antagonist, and clock gene regulator. Therefore, we propose ferroptosis as the culprit behind the post-COVID-19 trajectory of aging and neurodegeneration and melatonin, a well-fitting ferroptosis inhibitor, as a potential treatment.

SIEVE: One-stop differential expression, variability, and skewness analyses using RNA-Seq data

Motivation

RNA-Seq data analysis is commonly biased towards detecting differentially expressed genes and insufficiently conveys the complexity of gene expression changes between biological conditions. This bias arises because discrete models of RNA-Seq count data cannot fully characterize the mean, variance, and skewness of gene expression distribution using independent model parameters. A unified framework that simultaneously tests for differential expression, variability, and skewness is needed to realize the full potential of RNA-Seq data analysis in a systems biology context.

Results

We present SIEVE, a statistical methodology that provides the desired unified framework. SIEVE embraces a compositional data analysis framework that transforms discrete RNA-Seq counts to a continuous form with a distribution that is well-fitted by a skew-normal distribution. Simulation results show that SIEVE controls the false discovery rate and probability of Type II error better than existing methods for differential expression analysis. Analysis of the Mayo RNA-Seq dataset for Alzheimer's disease using SIEVE reveals that a gene set with significant expression difference in mean, standard deviation and skewness between the control and the Alzheimer's disease group strongly predicts a subject's disease state. Furthermore, functional enrichment analysis shows that relying solely on differentially expressed genes detects only a segment of a much broader spectrum of biological aspects associated with Alzheimer's disease. The latter aspects can only be revealed using genes that show differential variability and skewness. Thus, SIEVE enables fresh perspectives for understanding the intricate changes in gene expression that occur in complex diseases.

Availability

The SIEVE R package and source codes are available at https://github.com/Divo-Lee/SIEVE .

Do microbes play a role in Alzheimer's disease?

Alzheimer's disease is a complex and progressive condition that affects essential neurological functions such as memory and reasoning. In the brain, neuronal loss, synaptic dysfunction, proteinopathy, neurofibrillary tangles, and neuroinflammation are the hallmarks of Alzheimer's disease pathophysiology. In addition, recent evidence has highlighted that microbes, whether commensal or pathogenic, also have the ability to interact with their host and to regulate its immune system, therefore participating in the exchanges that lead to peripheral inflammation and neuropathology. Because of this intimate relationship, bacteria, viruses, fungi, and protozoa have been implicated in the development of Alzheimer's disease. Here, we bring together current and most recent evidence of the role of microbes in Alzheimer's disease, raising burning questions that need to be addressed to guide therapeutic approaches and potential prophylactic strategies.

Recent understanding of the mechanisms of the biological activities of hesperidin and hesperetin and their therapeutic effects on diseases

Flavonoids are natural phytochemicals that have therapeutic effects and act in the prevention of several pathologies. These phytochemicals can be found in lemon, sweet orange, bitter orange, clementine. Hesperidin and hesperetin are citrus flavonoids from the flavanones subclass that have anti-inflammatory, antioxidant, antitumor and antibacterial potential. Preclinical studies and clinical trials demonstrated therapeutical effects of hesperidin and its aglycone hesperetin in various diseases, such as bone diseases, cardiovascular diseases, neurological diseases, respiratory diseases, digestive diseases, urinary tract diseases. This review provides a comprehensive overview of the biological activities of hesperidin and hesperetin, their therapeutic potential in various diseases and their associated molecular mechanisms. This article also discusses future considerations for the clinical applications of hesperidin and hesperetin.

Withania somnifera (L.) Dunal, a Potential Source of Phytochemicals for Treating Neurodegenerative Diseases: A Systematic Review

Withania somnifera (L.) Dunal is a medicinal plant belonging to the traditional Indian medical system, showing various therapeutic effects such as anti-cancer, anti-inflammatory, anti-microbial, anti-diabetic, and hepatoprotective activity. Of great interest is W. somnifera's potential beneficial effect against neurodegenerative diseases, since the authorized medicinal treatments can only delay disease progression and provide symptomatic relief and are not without side effects. A systematic search of PubMed and Scopus databases was performed to identify preclinical and clinical studies focusing on the applications of W. somnifera in preventing neurodegenerative diseases. Only English articles and those containing the keywords (Withania somnifera AND "neurodegenerative diseases", "neuroprotective effects", "Huntington", "Parkinson", "Alzheimer", "Amyotrophic Lateral Sclerosis", "neurological disorders") in the title or abstract were considered. Reviews, editorials, letters, meta-analyses, conference papers, short surveys, and book chapters were not considered. Selected articles were grouped by pathologies and summarized, considering the mechanism of action. The quality assessment and the risk of bias were performed using the Cochrane Handbook for Systematic Reviews of Interventions checklist. This review uses a systematic approach to summarize the results from 60 investigations to highlight the potential role of W. somnifera and its specialized metabolites in treating or preventing neurodegenerative diseases.

Cellular junction dynamics and Alzheimer's disease: a comprehensive review

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by progressive neuronal damage and cognitive decline. Recent studies have shed light on the involvement of not only the blood-brain barrier (BBB) dysfunction but also significant alterations in cellular junctions in AD pathogenesis. In this review article, we explore the role of the BBB and cellular junctions in AD pathology, with a specific focus on the hippocampus. The BBB acts as a crucial protective barrier between the bloodstream and the brain, maintaining brain homeostasis and regulating molecular transport. Preservation of BBB integrity relies on various junctions, including gap junctions formed by connexins, tight junctions composed of proteins such as claudins, occludin, and ZO-1, as well as adherence junctions involving molecules like vascular endothelial (VE) cadherin, Nectins, and Nectin-like molecules (Necls). Abnormalities in these junctions and junctional components contribute to impaired neuronal signaling and increased cerebrovascular permeability, which are closely associated with AD advancement. By elucidating the underlying molecular mechanisms governing BBB and cellular junction dysfunctions within the context of AD, this review offers valuable insights into the pathogenesis of AD and identifies potential therapeutic targets for intervention.

Improvement of Key Molecular Events Linked to Alzheimer's Disease Pathology Using Postbiotics

In the past 50 years, life expectancy has increased by more than 20 years. One consequence of this increase in longevity is the rise of age-related diseases such as dementia. Alzheimer's disease (AD) is the most common form of dementia, accounting for 60-70% of cases. AD pathogenesis is not restricted to the neuronal compartment but includes strong interactions with other brain cells, particularly microglia triggering the release of inflammatory mediators, which contribute to disease progression and severity. There is growing evidence revealing the diverse clinical benefits of postbiotics in many prevalent conditions, including neurodegenerative diseases. Here, we tested the ability of bacterial conditioned media (BCM) derived from selected lactic acid bacteria (LAB) strains to regulate core mechanisms relevant to AD pathophysiology in the microglia cell line BV-2. Levilactobacillus brevis CRL 2013, chosen for its efficient production of the neurotransmitter GABA, and Lactobacillus delbrueckii subsp. lactis CRL 581, known for its anti-inflammatory properties, were selected alongside Enterococcus mundtii CRL 35, a LAB strain that can significantly modulate cytokine production. BCM from all 3 strains displayed antioxidant capabilities, reducing oxidative stress triggered by beta-amyloid oligomers (oAβ1-42). Additionally, BCM effectively mitigated the expression of inflammatory cytokines, namely, TNF-α, IL-1β, and IL-6 triggered by oAβ1-42. Furthermore, our study identified that BCM from CRL 581 inhibit the activity of acetylcholinesterase (AChE), a crucial enzyme in AD progression, in both human erythrocytes and mouse brain tissues. Notably, the inhibitory effect was mediated by low-molecular-weight components of the BCM. L. delbrueckii subsp. lactis CRL 581 emerged as a favorable candidate for production of postbiotics with potential benefits for AD therapy since it demonstrated potent antioxidant activity, reduction of cytokine expression, and partial AChE inhibition. On the other hand, E. mundtii CRL 35 showed that the antioxidant activity failed to inhibit AChE and caused induction of iNOS expression, rendering it unsuitable as a potential therapeutic for AD. This study unveils the potential benefits of LAB-derived postbiotics for the development of new avenues for therapeutic interventions for AD.

Multifunctional Supramolecular Vesicles as Zn2+ -Triggered Microglial Modulator Alleviates Alzheimer's Disease

Zn2+ -induced β-amyloid protein (Aβ) aggregation and microglia activation are the predominant contributors in Alzheimer's disease (AD). Regulating intracephalic excessive Zn2+ is a promising therapeutic strategy for AD treatment. However, only inhibition of Zn2+ is hardly to repair continuous damages caused by activated microglia. Herein, an intelligent resveratrol-loaded supramolecular vesicles (RES-loaded vesicles) with zinc ion chelation function and responsive release capability are constructed to alleviate Aβ fibrillation, oxidative stress, and microglial dysfunction. The resveratrol encapsulation efficiency and drug loading efficiency are calculated to be 49.67% and 7.87%, respectively. In vitro studies demonstrate that the RES-loaded vesicles can modulate Zn2+ -dependent Aβ aggregation. More importantly, the cargoes will be released in zinc environment and further reprograms microglia from proinflammatory M1 phenotype toward anti-inflammatory M2 phenotype, which prevents spontaneous neuroinflammation and alleviates cytotoxicity of cultured cells from 29% to 12%. With the stereotactic or intranasal administration, RES-loaded vesicles can overcome the blood brain barrier, alleviate neuronal apoptosis, neuroinflammation, and ultimately ameliorate cognitive impairment in two AD mouse models. This work provides a new sight for taking advantage of Zn2+ to treat CNS disorders.

Nattokinase prevents β-amyloid peptide (Aβ1-42) induced neuropsychiatric complications, neuroinflammation and BDNF signalling disruption in mice

Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disorder characterized by abnormal accumulation of extracellular β-amyloid (Aβ) plaques and neuronal damage. Although AD is typically considered a cognitive neurodegenerative disorder, almost all people diagnosed with AD develop neuropsychiatric complications at some stage in their life span. The present study investigated the effect of chronic Nattokinase (NK) administration on β-Amyloid peptide (Aβ1-42) induced neuropsychiatric conditions (depression-like behaviour, anxiety, and memory impairment) in mice. Aβ1-42 peptide injected mice demonstrated depression, anxiety, and impairment of cognitive abilities evaluated as increased immobility time in forced swim test (FST), decreased open arm time/entries in elevated plus maze (EPM) and reference and working memory error in radial arm maze (RAM) respectively with elevation in Interleukin-6 (IL-6), Tumour necrosis factor-α (TNF-α), reduction in Interleukin-10 (IL-10) and Brain-derived neurotrophic factor (BDNF) immunocontent within the hippocampus. Chronic administration of NK (50-100 mg/kg, i.p.) from day 8-27, prevented depression-like behaviour, anxiety, and memory impairment and normalized the neurochemical alteration within the hippocampus of mice injected with Aβ1-42 peptide. The effect of NK on psychiatric complications, learning, and memory was comparable to peripheral donepezil treatment. This study suggests that NK improves learning, memory impairment, and neuropsychiatric complications possibly through the downregulation of neuroinflammatory pathways and restoring BDNF signalling in AD.

Potential neuroprotective effects of fermented foods and beverages in old age: a systematic review

Purpose

Numerous articles have recently studied the involvement of the gut microbiota in neurological diseases. Aging is associated with changes in the microbiome, which implies a reduction in microbial biodiversity among other changes. Considering that the consumption of a fermented-food diet improves intestinal permeability and barrier function, it seems of interest to study its participation in the prevention of neurodegenerative diseases. This article reviews existing studies to establish whether the consumption of fermented foods and fermented beverages prevents or ameliorates neurodegenerative decline in old age.

Methods

The protocol used was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Details of the protocol for this systematic review are registered on PROSPERO (CRD42021250921).

Results

Out of 465 articles identified in the Pubmed, Scopus, and Cochrane Library databases, a total of 29 that examined the relationship of the consumption of fermented products with cognitive impairment in old people were selected (22 cohort, 4 case-control, and 3 cross-sectional studies). The results suggest that low-to-moderate alcohol consumption and daily intake of coffee, soy products, and fermented-food diets in general are associated with a lower risk of dementia and Alzheimer's disease.

Conclusion

Daily consumption of fermented foods and beverages, either alone or as part of a diet, has neuroprotective effects and slows cognitive decline in old people.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=250921, identifier: CRD42021250921.

Benzene, 1,2,4-trimethoxy-5-(2-methyl-1-propen-1-yl) Attenuates D-galactose /AlCl3-induced Cognitive Impairment by Inhibiting Inflammation, Apoptosis, and Improving ExpressionofMemory-Related Proteins

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by decreased learning ability and memory deficits. Our previous findings suggested that benzene, 1,2,4-trimethoxy-5-(2-methyl-1-propen-1-yl) (BTY) can ameliorate the dysfunction of GABAergic inhibitory neurons associated with neurological diseases. On this basis, we investigated the neuroprotective effect of BTY on AD and explored the underlying mechanism. This study included in vitro and in vivo experiments. BTY could maintain cell morphology, improve cell survival rate, reduce cell damage, and inhibit cell apoptosis in vitro experiments. Further, BTY has good pharmacological activity in vivo experiments, of which behavioral experiments showed that BTY could improve AD-like mice's learning and memory abilities. Besides, histopathological experiments indicated that BTY could maintain the morphology and function of neurons, reduce amyloid β-protein 42 (Aβ₄₂) and phosphorylated tau (p-tau) accumulation, and decrease the levels of inflammatory cytokines. Finally, western blot experiments showed that BTY could inhibit the expression of apoptosis-related proteins and promote the expression of memory-related proteins. In conclusion, this study indicated that BTY may be a promising drug candidate for AD.

Trends of mitochondrial changes in AD: a bibliometric study

Background

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive progress and memory loss, which eventually develops into dementia. It can cause personality disorders and decreased quality of life of patients. Currently, AD patients account for 60-70% of global dementia patients and the incidence rate of AD is increasing annually. AD not only causes pain to patients but also brings a heavy burden to the entire family. Studies have found that there is a connection between mitochondrial dysfunction and other biochemical changes in AD like classical neuropathological hallmarks (β-amyloid and tau protein), inflammation pathways, oxidative stress, and so on. Evidence shows that early treatment targeted directly to mitochondria could extend the lifespan of model mice and decrease the relevant neuropathological markers. Therefore, research on the mitochondrial dysfunction of AD can be of potential significance for clinical treatment. To date, few bibliometric analysis articles related to mitochondrial dysfunction of AD have been published. Bibliometric analysis refers to quantitatively analyzing certain aspects of articles like publishers, authors, and countries by using statistical and mathematical methods. Combined with statistical software, a large number of papers can be converted to visualization figures and tables, which provide vital information such as keyword hotspots and the names of contributing authors. Through the bibliometric analysis method, our study aimed to provide study trends and keyword hotpots for researchers to conduct further relevant research in this field.

Methods

We used the Web of Science core collection database as a literature retrieval tool to obtain data related to mitochondrial changes in Alzheimer's disease during the last 20 years. The retrieval type was [TS = (Alzheimer's disease)] ND [TS = (mitochondrion)], ranging from January 1, 2000 to June 30, 2022. VOSviewer v1.6.18, Arcgis 10.8, and HistCite pro 2.1 were used to conduct data visualization analysis. VOSviewer v1.6.18 made relevant network visualization maps of the cooperative relationship between relevant countries, institutions, and authors (co-authorship), the frequency of different keywords appearing together (co-occurrence), and the frequency of different articles cited together (co-cited). Arcgis 10.8 created the world map of publications distribution in this field and Histcite pro 2.1 was used to count the local citation score (LCS) of references. In addition, Journal Citation Reports were used to consult the latest journal import factor and JCI quartile.

Results

As of June 30, 2022, from the Web of Science core collection, we selected 2,474 original articles in English, excluding the document types of the news items, meeting abstracts, and some articles that had little relevance to our theme. The United States acted as the leader and enjoyed a high reputation in this field. The University of California System was the institution that made the greatest contribution (3.64% with 90 papers). Most articles were published in the Journal of Alzheimer's Disease (8.21%, with 203 papers). The most frequently co-cited journal in Q1 was the Journal of Biological Chemistry (8,666 citations, TLS: 1039591). Russel H. Swerdlow (55 publications) was the most productive author and PH Reddy was the most co-cited author with 1,264 citations (TLS: 62971). The hotpots of mitochondrial dysfunction in AD were as follows: "oxidative stress," "amyloid-beta-protein," "tau," "apoptosis," "inflammation," "autophagy," "precursor protein," "endoplasmic-reticulum," "dynamics" and "mitochondrial unfolded protein response."

Conclusion

This bibliometric analysis research will help readers rapidly identify current hotpots and milestone studies related to directions of interest in AD research.

Brain-targeted lycopene-loaded microemulsion modulates neuroinflammation, oxidative stress, apoptosis and synaptic plasticity in β-amyloid-induced Alzheimer's disease mice

OBJECTIVES

β-Amyloid protein (Aβ) plays pivotal roles in pathogenesis of Alzheimer's disease (AD) and triggers various pathophysiological events. Lycopene is a promising neuroprotector with multiple bioactivities, while its bioavailability is limited. Lycopene-loaded microemulsion (LME) possessing superior bioavailability and brain-targeting efficiency was developed in our previous study. In this investigation, we aimed to comprehensively evaluate its neuroprotective effects and underlying mechanisms using intracerebroventricular (ICV) Aβ_1-42 injection mice.

METHODS

Mice were assigned to the Sham, Aβ, Aβ + LME and Aβ + lycopene dissolved in olive oil (LOO) groups. ICV Aβ_1-42 administration was performed, followed by oral gavage of brain-targeted LME or conventional LOO formulation for 3 weeks. Brain samples were harvested for immunohistochemistry, biochemical assays and western blotting analyses.

RESULTS

Our findings verified Aβ-induced neurotoxicity on neuroinflammation, oxidative stress, apoptosis, Aβ metabolisms and synaptic plasticity. LME supplementation dramatically attenuated astrocytosis and microgliosis, decreased malondialdehyde production and rescued antioxidant capacities, normalized apoptotic parameters and alleviated neuronal loss, inhibited amyloidogenic processing and activated non-amyloidogenic pathway, together with upregulating synaptic protein expressions and restoring synaptic plasticity. Nevertheless, most of these phenomena were not observed for mice treated with LOO, implying that LME showed significantly higher therapeutic efficacy against Aβ injury.

DISCUSSION

In summary, brain-targeted LME could exert neuroprotective function via suppressing a series of cascades triggered by Aβ aggregates, thus ameliorating Aβ neurotoxicity and associated abnormalities. Given this, LME may serve as an attractive candidate for AD prevention and treatment, and superiority of brain-targeting delivery is highlighted.

Strategies for Manipulating Microglia to Determine Their Role in the Healthy and Diseased Brain

Microglia are the specialized macrophages of the central nervous system and play an important role in neural circuit development, modulating neurotransmission, and maintaining brain homeostasis. Microglia in normal brain is quiescent and show ramified morphology with numerous branching processes. They constantly survey their surrounding microenvironment through the extension and retraction of their processes and interact with neurons, astrocytes, and blood vessels using these processes. Microglia respond quickly to any pathological event in the brain by assuming ameboid morphology devoid of branching processes and restore homeostasis. However, when there is chronic inflammation, microglia may lose their homeostatic functions and secrete various proinflammatory cytokines and mediators that initiate neural dysfunction and neurodegeneration. In this article, we review the role of microglia in the normal brain and in various pathological brain conditions, such as Alzheimer's disease and multiple sclerosis. We describe strategies to manipulate microglia, focusing on depletion, repopulation, and replacement, and we discuss their therapeutic potential.

Possible Implications of Obesity-Primed Microglia that Could Contribute to Stroke-Associated Damage

Microglia, the resident macrophages of the central nervous system, are essential players during physiological and pathological processes. Although they participate in synaptic pruning and maintenance of neuronal circuits, microglia are mainly studied by their activity modulating inflammatory environment and adapting their phenotype and mechanisms to insults detected in the brain parenchyma. Changes in microglial phenotypes are reflected in their morphology, membrane markers, and secreted substances, stimulating neighbor glia and leading their responses to control stimuli. Understanding how microglia react in various microenvironments, such as chronic inflammation, made it possible to establish therapeutic windows and identify synergic interactions with acute damage events like stroke. Obesity is a low-grade chronic inflammatory state that gradually affects the central nervous system, promoting neuroinflammation development. Obese patients have the worst prognosis when they suffer a cerebral infarction due to basal neuroinflammation, then obesity-induced neuroinflammation could promote the priming of microglial cells and favor its neurotoxic response, potentially worsening patients' prognosis. This review discusses the main microglia findings in the obesity context during the course and resolution of cerebral infarction, involving the temporality of the phenotype changes and balance of pro- and anti-inflammatory responses, which is lost in the swollen brain of an obese subject. Obesity enhances proinflammatory responses during a stroke. Obesity-induced systemic inflammation promotes microglial M₁ polarization and priming, which enhances stroke-associated damage, increasing M₁ and decreasing M₂ responses.

Extract of Aster koraiensis Nakai Leaf Ameliorates Memory Dysfunction via Anti-inflammatory Action

Aster koraiensis Nakai (AK) leaf reportedly ameliorates health problems, such as diabetes. However, the effects of AK on cognitive dysfunction or memory impairment remain unclear. This study investigated whether AK leaf extract could attenuate cognitive impairment. We found that AK extract reduced the production of nitric oxide (NO), tumour necrosis factor (TNF)-α, phosphorylated-tau (p-tau), and the expression of inflammatory proteins in lipopolysaccharide- or amyloid-β-treated cells. AK extract exhibited inhibitory activity of control specific binding on N-methyl-D-aspartate (NMDA) receptors. Scopolamine-induced AD models were used chronically in rats and acutely in mice. Relative to negative controls (NC), hippocampal choline acetyltransferase (ChAT) and B-cell lymphoma 2 (Bcl2) activity was increased in rats chronically treated with scopolamine and fed an AK extract-containing diet. In the Y-maze test, spontaneous alterations were increased in the AK extract-fed groups compared to NC. Rats administered AK extract showed increased escape latency in the passive avoidance test. In the hippocampus of rats fed a high-AK extract diet (AKH), the expression of neuroactive ligand–receptor interaction-related genes, including Npy2r, Htr2c, and Rxfp1, was significantly altered. In the Morris water maze assay of mice acutely treated with scopolamine, the swimming times in the target quadrant of AK extract-treated groups increased significantly to the levels of the Donepezil and normal groups. We used Tg6799 Aβ-overexpressing 5XFAD transgenic mice to investigate Aβ accumulation in animals. In the AD model using 5XFAD, the administration of AK extract decreased amyloid-β (Aβ) accumulation and increased the number of NeuN antibody-reactive cells in the subiculum relative to the control group. In conclusion, AK extract ameliorated memory dysfunction by modulating ChAT activity and Bcl2-related anti-apoptotic pathways, affecting the expression of neuroactive ligand–receptor interaction-related genes and inhibiting Aβ accumulation. Therefore, AK extract could be a functional material improving cognition and memory.

ACAT1/SOAT1 Blockade Suppresses LPS-Mediated Neuroinflammation by Modulating the Fate of Toll-like Receptor 4 in Microglia

Cholesterol is stored as cholesteryl esters by the enzymes acyl-CoA:cholesterol acyltransferases/sterol O:acyltransferases (ACATs/SOATs). ACAT1 blockade (A1B) ameliorates the pro-inflammatory responses of macrophages to lipopolysaccharides (LPS) and cholesterol loading. However, the mediators involved in transmitting the effects of A1B in immune cells is unknown. Microglial Acat1/Soat1 expression is elevated in many neurodegenerative diseases and in acute neuroinflammation. We evaluated LPS-induced neuroinflammation experiments in control vs. myeloid-specific Acat1/Soat1 knockout mice. We also evaluated LPS-induced neuroinflammation in microglial N9 cells with and without pre-treatment with K-604, a selective ACAT1 inhibitor. Biochemical and microscopy assays were used to monitor the fate of Toll-Like Receptor 4 (TLR4), the receptor at the plasma membrane and the endosomal membrane that mediates pro-inflammatory signaling cascades. In the hippocampus and cortex, results revealed that Acat1/Soat1 inactivation in myeloid cell lineage markedly attenuated LPS-induced activation of pro-inflammatory response genes. Studies in microglial N9 cells showed that pre-incubation with K-604 significantly reduced the LPS-induced pro-inflammatory responses. Further studies showed that K-604 decreased the total TLR4 protein content by increasing TLR4 endocytosis, thus enhancing the trafficking of TLR4 to the lysosomes for degradation. We concluded that A1B alters the intracellular fate of TLR4 and suppresses its pro-inflammatory signaling cascade in response to LPS.

Single-cell RNA-sequencing identifies disease-associated oligodendrocytes in male APP NL-G-F and 5XFAD mice

Alzheimer's disease (AD) is associated with progressive neuronal degeneration as amyloid-beta (Aβ) and tau proteins accumulate in the brain. Glial cells were recently reported to play an important role in the development of AD. However, little is known about the role of oligodendrocytes in AD pathogenesis. Here, we describe a disease-associated subpopulation of oligodendrocytes that is present during progression of AD-like pathology in the male App^NL-G-F and male 5xFAD AD mouse brains and in postmortem AD human brains using single-cell RNA sequencing analysis. Aberrant Erk1/2 signaling was found to be associated with the activation of disease-associated oligodendrocytes (DAOs) in male App^NL-G-F mouse brains. Notably, inhibition of Erk1/2 signaling in DAOs rescued impaired axonal myelination and ameliorated Aβ-associated pathologies and cognitive decline in the male App^NL-G-F AD mouse model.

Effects of Peroxisome Proliferator-Activated Receptor-Gamma Agonists on Cognitive Function: A Systematic Review and Meta-Analysis

Diabetes mellitus (DM) is known to be a risk factor for dementia, especially in the elderly population, and close associations between diabetes and Alzheimer disease (AD) have been determined. Peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonists are insulin-sensitising drugs. In addition to their anti-diabetic properties, their effectiveness in preventing and decreasing cognitive impairment are the most recent characteristics that have been studied. For this study, we conducted a systematic review and meta-analysis to critically analyse and evaluate the existing data on the effects of PPAR-γ agonist therapy on the cognitive status of patients. For this purpose, we first analysed both early intervention and later treatment with PPAR-γ agonists, according to the disease status. The involved studies indicated that early PPAR-γ agonist intervention is beneficial for patients and that high-dose PPAR-γ therapy may have a better clinical effect, especially in reversing the effects of cognitive impairment. Furthermore, the efficacy of pioglitazone (PIO) seems to be promising, particularly for patients with comorbid diabetes. PIO presented a better clinical curative effect and safety, compared with rosiglitazone (RSG). Thus, PPAR-γ agonists play an important role in the inflammatory response of AD or DM patients, and clinical therapeutics should focus more on relevant metabolic indices.

The Inflammatory Gene PYCARD of the Entorhinal Cortex as an Early Diagnostic Target for Alzheimer's Disease

The incidence of Alzheimer's disease (AD) is increasing year by year, which brings great challenges to human health. However, the pathogenesis of AD is still unclear, and it lacks early diagnostic targets. The entorhinal cortex (EC) is a key brain region for the occurrence of AD neurodegeneration, and neuroinflammation plays a significant role in EC degeneration in AD. This study aimed to reveal the close relationship between inflammation-related genes in the EC and AD by detecting key differentially expressed genes (DEGs) via gene function enrichment pathway analysis. GSE4757 and GSE21779 gene expression profiles of AD were downloaded from the Gene Expression Omnibus (GEO) database. R language was used for the standardization and differential analysis of DEGs. Then, significantly enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were analyzed to predict the potential biological functions of the DEGs. Finally, the significant expressions of identified DEGs were verified, and the therapeutic values were detected by a receiver operating characteristic (ROC) curve. The results showed that eight up-regulated genes (SLC22A2, ITGB2-AS1, NIT1, FGF14-AS2, SEMA3E, PYCARD, PRORY, ADIRF) and two down-regulated genes (AKAIN1, TRMT2B) may have a potential diagnostic value for AD, and participate in inflammatory pathways. The area under curve (AUC) results of the ten genes showed that they had potential diagnostic value for AD. The AUC of PYCARD was 0.95, which had the most significant diagnostic value, and it is involved in inflammatory processes such as the inflammasome complex adaptor protein. The DEGs screened, and subsequent pathway analysis revealed a close relationship between inflammation-related PYCARD and AD, thus providing a new basis for an early diagnostic target for AD.

The Role of T Cells in Alzheimer's Disease Pathogenesis

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with memory decline and cognitive impairment, which is related to hallmark protein aggregates, amyloid-β (Аβ) plaques and neurofibrillary tangles; the latter are accumulated with hyperphosphorylated Tau protein. Immune cells play an important role in AD pathogenesis. Although the role of T cells in AD remains controversial, studies have shown that T cell deficiency is associated with increased AD pathology. In contrast, transplantation of T cells reduces AD pathology. T cells can help B cells generate anti-Аβ antibody to neutralize the toxin of Аβ and hyperphosphorylated Tau. T cells also activate macrophages to phagocytose misfolded proteins including Аβ and Tau. Recent data have also shown that AD animals have a damaged thymic microenvironment, especially thymic epithelial cells (TECs), resulting in decreased T cell numbers, which contribute to AD pathology. Therefore, regulation of T cell regeneration, for example by rejuvenating the thymic microenvironment, has the potential to be used in the treatment of AD.

Applications of Induced Pluripotent Stem Cell-Derived Glia in Brain Disease Research and Treatment

Glia are integral components of neural networks and are crucial in both physiological functions and pathological processes of the brain. Many brain diseases involve glial abnormalities, including inflammatory changes, mitochondrial damage, calcium signaling disturbance, hemichannel opening, and loss of glutamate transporters. Induced pluripotent stem cell (iPSC)-derived glia provide opportunities to study the contributions of glia in human brain diseases. These cells have been used for human disease modeling as well as generating new therapies. This chapter introduces glial involvement in brain diseases, then summarizes different methods of generating iPSC-derived glia disease models of these cells. Finally, strategies for treating disease using iPSC-derived glia are discussed. The goal of this chapter is to provide an overview and shed light on the applications of iPSC-derived glia in brain disease research and treatment.

Transferrin Enhances Neuronal Differentiation

Although transferrin (Tf) is a glycoprotein best known for its role in iron delivery, iron-independent functions have also been reported. Here, we assessed apoTf (aTf) treatment effects on Neuro-2a (N2a) cells, a mouse neuroblastoma cell line which, once differentiated, shares many properties with neurons, including process outgrowth, expression of selective neuronal markers, and electrical activity. We first examined the binding of Tf to its receptor (TfR) in our model and verified that, like neurons, N2a cells can internalize Tf from the culture medium. Next, studies on neuronal developmental parameters showed that Tf increases N2a survival through a decrease in apoptosis. Additionally, Tf accelerated the morphological development of N2a cells by promoting neurite outgrowth. These pro-differentiating effects were also observed in primary cultures of mouse cortical neurons treated with aTf, as neurons matured at a higher rate than controls and showed a decrease in the expression of early neuronal markers. Further experiments in iron-enriched and iron-deficient media showed that Tf preserved its pro-differentiation properties in N2a cells, with results hinting at a modulatory role for iron. Moreover, N2a-microglia co-cultures revealed an increase in IL-10 upon aTf treatment, which may be thought to favor N2a differentiation. Taken together, these findings suggest that Tf reduces cell death and favors the neuronal differentiation process, thus making Tf a promising candidate to be used in regenerative strategies for neurodegenerative diseases.

Multifactorial Causation of Alzheimer's Disease Due to COVID-19

There are several implications of the surge in the incidence of pandemics and epidemics in the last decades. COVID-19 being the most remarkable one, showed the vulnerability of patients with neurodegenerative diseases like Alzheimer's disease (AD). This review studies the pathological interlinks and triggering factors between the two illnesses and proposes a multifactorial pathway of AD causation due to COVID-19. The article evaluates and describes all the postulated hypotheses which explain the etiology and possible pathogenesis of the disease in four domains: Inflammation & Neurobiochemical interactions, Oxidative Stress, Genetic Factors, and Social Isolation. We believe that a probable hypothesis of an underlying cause of AD after COVID-19 infection could be the interplay of all these factors.

S100A9 amyloid growth and S100A9 fibril-induced impairment of gamma oscillations in area CA3 of mouse hippocampus ex vivo is prevented by Bri2 BRICHOS

The pro-inflammatory and highly amyloidogenic protein S100A9 is central to the amyloid-neuroinflammatory cascade in neurodegenerative diseases leading to cognitive impairment. Molecular chaperone activity of Bri2 BRICHOS has been demonstrated against a range of amyloidogenic polypeptides. Using a combination of thioflavin T fluorescence kinetic assay, atomic force microscopy and immuno electron microscopy we show here that recombinant Bri2 BRICHOS effectively inhibits S100A9 amyloid growth by capping amyloid fibrils. Using ex-vivo neuronal network electrophysiology in mouse brain slices we also show that both native S100A9 and amyloids of S100A9 disrupt cognition-relevant gamma oscillation power and rhythmicity in hippocampal area CA3 in a time- and protein conformation-dependent manner. Both effects were associated with Toll-like receptor 4 (TLR4) activation and were not observed upon TLR4 blockade. Importantly, S100A9 that had co-aggregated with Bri2 BRICHOS did not elicit degradation of gamma oscillations. Taken together, this work provides insights on the potential influence of S100A9 on cognitive dysfunction in Alzheimer's disease (AD) via gamma oscillation impairment from experimentally-induced gamma oscillations, and further highlights Bri2 BRICHOS as a chaperone against detrimental effects of amyloid self-assembly.

Morphological and biomolecular targets in retina and vitreous from Reelin-deficient mice (Reeler): Potential implications for age-related macular degeneration in Alzheimer’s dementia

The neurosensory retina is an outgrowth of the Central Nervous System (CNS), and the eye is considered “a window to the brain.” Reelin glycoprotein is directly involved in neurodevelopment, in synaptic plasticity, learning and memory. Consequently, abnormal Reelin signaling has been associated with brain neurodegeneration but its contributing role in ocular degeneration is still poorly explored. To this aim, experimental procedures were assayed on vitreous or retinas obtained from Reeler mice (knockout for Reelin protein) at different postnatal days (p) p14, p21 and p28. At p28, a significant increase in the expression of Amyloid Precursor Protein (APP) and its amyloidogenic peptide (Aβ1-42 along with truncated tau fragment (i.e., NH2htau)- three pathological hallmarks of Alzheimer’s disease (AD)-were found in Reeler mice when compared to their age-matched wild-type controls. Likewise, several inflammatory mediators, such as Interleukins, or crucial biomarkers of oxidative stress were also found to be upregulated in Reeler mice by using different techniques such as ELLA assay, microchip array or real-time PCR. Taken together, these findings suggest that a dysfunctional Reelin signaling enables the expression of key pathological features which are classically associated with AD neurodegenerative processes. Thus, this work suggests that Reeler mouse might be a suitable animal model to study not only the pathophysiology of developmental processes but also several neurodegenerative diseases, such as AD and Age-related Macular Degeneration (AMD), characterized by accumulation of APP and/or Aβ1-42, NH2htau and inflammatory markers.

Circulating extracellular vesicle-containing microRNAs reveal potential pathogenesis of Alzheimer’s disease

The pathogenesis of Alzheimer’s disease (AD) remains unknown till today, hindering the research and development of AD therapeutics and diagnostics. Circulating extracellular vesicles (EVs) can be utilized as a new window to spy upon AD pathogenesis. Altered microRNA profiles were noted in both the cerebrospinal fluid (CSF)- and blood-isolated EVs of AD patients, implying the outstanding potential of circulating EV-containing miRNAs (CEmiRs) to serve as important regulators in AD pathogenesis. Although several CEmiRs were found to play a part in AD, the association of globally altered miRNA profiles in patients’ serum-derived EVs with AD pathogenesis remains unclear. In this study, we first investigated the miRNA profile in serum-derived EVs from AD, mild cognitive impairment (MCI) patients, and healthy individuals. We observed differential expression patterns of CEmiRs and classified them into 10 clusters. We identified the predicted targets of these differentially expressed CEmiRs (DECEmiRs) and analyzed their biological functions and interactions. Our study revealed the temporal regulation of complex and precise signaling networks on AD pathogenesis, shedding light on the development of novel therapeutic strategies, including multi-target drug combination for AD treatment.

Microglia: Friend and foe in tauopathy

Aggregation of misfolded microtubule associated protein tau into abnormal intracellular inclusions defines a class of neurodegenerative diseases known as tauopathies. The consistent spatiotemporal progression of tau pathology in Alzheimer's disease (AD) led to the hypothesis that tau aggregates spread in the brain via bioactive tau "seeds" underlying advancing disease course. Recent studies implicate microglia, the resident immune cells of the central nervous system, in both negative and positive regulation of tau pathology. Polymorphisms in genes that alter microglial function are associated with the development of AD and other tauopathies. Experimental manipulation of microglia function can alter tau pathology and microglia-mediated neuroinflammatory cascades can exacerbate tau pathology. Microglia also exert protective functions by mitigating tau spread: microglia internalize tau seeds and have the capacity to degrade them. However, when microglia fail to degrade these tau seeds there are deleterious consequences, including secretion of exosomes containing tau that can spread to neurons. This review explores the intersection of microglia and tau from the perspective of neuropathology, neuroimaging, genetics, transcriptomics, and molecular biology. As tau-targeted therapies such as anti-tau antibodies advance through clinical trials, it is critical to understand the interaction between tau and microglia.

A2A Adenosine Receptor: A Possible Therapeutic Target for Alzheimer's Disease by Regulating NLRP3 Inflammasome Activity?

The A2A adenosine receptor, a member of the P1 purinergic receptor family, plays a crucial role in the pathophysiology of different neurodegenerative illnesses, including Alzheimer’s disease (AD). It regulates both neurons and glial cells, thus modulating synaptic transmission and neuroinflammation. AD is a complex, progressive neurological condition that is the leading cause of dementia in the world’s old population (>65 years of age). Amyloid peptide-β extracellular accumulation and neurofibrillary tangles constitute the principal etiologic tracts, resulting in apoptosis, brain shrinkage, and neuroinflammation. Interestingly, a growing body of evidence suggests a role of NLRP3 inflammasome as a target to treat neurodegenerative diseases. It represents a tripartite multiprotein complex including NLRP3, ASC, and procaspase-1. Its activation requires two steps that lead with IL-1β and IL-18 release through caspase-1 activation. NLRP3 inhibition provides neuroprotection, and in recent years adenosine, through the A2A receptor, has been reported to modulate NLRP3 functions to reduce organ damage. In this review, we describe the role of NLRP3 in AD pathogenesis, both alone and in connection to A2A receptor regulation, in order to highlight a novel approach to address treatment of AD.

Alzheimer’s Disease Biomarkers Revisited From the Amyloid Cascade Hypothesis Standpoint

Alzheimer’s disease (AD) is the most common neurodegenerative disease worldwide. Amyloid beta (Aβ) is one of the proteins which aggregate in AD, and its key role in the disease pathogenesis is highlighted in the amyloid cascade hypothesis, which states that the deposition of Aβ in the brain parenchyma is a crucial initiating step in the future development of AD. The sensitivity of instruments used to measure proteins in blood and cerebrospinal fluid has significantly improved, such that Aβ can now successfully be measured in plasma. However, due to the peripheral production of Aβ, there is significant overlap between diagnostic groups. The presence of pathological Aβ within the AD brain has several effects on the cells and surrounding tissue. Therefore, there is a possibility that using markers of tissue responses to Aβ may reveal more information about Aβ pathology and pathogenesis than looking at plasma Aβ alone. In this manuscript, using the amyloid cascade hypothesis as a starting point, we will delve into how the effect of Aβ on the surrounding tissue can be monitored using biomarkers. In particular, we will consider whether glial fibrillary acidic protein, triggering receptor expressed on myeloid cells 2, phosphorylated tau, and neurofilament light chain could be used to phenotype and quantify the tissue response against Aβ pathology in AD.

Eriodictyol and Homoeriodictyol Improve Memory Impairment in Aβ25–35-Induced Mice by Inhibiting the NLRP3 Inflammasome

(1) Alzheimer’s disease (AD) is a neurodegenerative disorder, and it is now widely accepted that neuroinflammation plays a key role in its pathogenesis. Eriodictyol (Eri) and homoeriodictyol (Hom), dihydroflavonoids extracted from a variety of plants, have been confirmed to display a relationship with neuroprotection. (2) Methods: An AD mouse model was constructed by intracerebroventricular (ICV) injection of the Aβ_25–35 peptide, and Eri and Hom were administered orally for 4 weeks. UPLC-MS/MS was used to determine whether Eri and Hom cross the blood–brain barrier to exert their therapeutic effects. Histological changes in the brain and levels of Aβ were evaluated, and Y-maze and new object recognition experiments were conducted to assess the effects of Eri and Hom on Aβ_25–35-induced memory impairment in mice. The levels of oxidative stress and apoptosis in peripheral immune cells and progenitor cells in the hippocampal region were analyzed by flow cytometry and in vitro assays. Western blotting and enzyme-linked immunosorbent assays (ELISA) were used to measure the expression levels of NLRP3 inflammasome-related proteins and inflammatory factors in the brain. The effect of nigericin (an agonist of the NLRP3 inflammasome) on Eri and Hom intervention in LPS-induced N9 microglia was examined using a High Content Screening System. (3) Results: Eri and Hom reduced neuronal damage in mouse brain tissue, decreased Aβ levels in the brain, downregulated oxidative stress and apoptosis levels, and improved learning and memory capacity by crossing the blood–brain barrier to exert its effects. Moreover, Eri and Hom inhibited NLRP3 inflammasome activation and ameliorated immune cell disorder. Furthermore, the effect of Eri and Hom on LPS-induced N9 microglia disappeared after the addition of nigericin to agonize NLRP3 receptors. (4) Conclusions: Eri and Hom improved Aβ_25–35-induced memory impairment in mice by inhibiting the NLRP3 inflammasome.

Potential Roles of Glucagon-Like Peptide-1 and Its Analogues in Dementia Targeting Impaired Insulin Secretion and Neurodegeneration

Dementia is a chronic, irreversible condition marked by memory loss, cognitive decline, and mental instability. It is clinically related to various progressive neurological diseases, including Parkinson’s disease, Alzheimer’s disease, and Huntington’s. The primary cause of neurological disorders is insulin desensitization, demyelination, oxidative stress, and neuroinflammation accompanied by various aberrant proteins such as amyloid-β deposits, Lewy bodies accumulation, tau formation leading to neurofibrillary tangles. Impaired insulin signaling is directly associated with amyloid-β and α-synuclein deposition, as well as specific signaling cascades involved in neurodegenerative diseases. Insulin dysfunction may initiate various intracellular signaling cascades, including phosphoinositide 3-kinase (PI3K), c-Jun N-terminal kinases (JNK), and mitogen-activated protein kinase (MAPK). Neuronal death, inflammation, neuronal excitation, mitochondrial malfunction, and protein deposition are all influenced by insulin. Recent research has focused on GLP-1 receptor agonists as a potential therapeutic target. They increase glucose-dependent insulin secretion and are beneficial in neurodegenerative diseases by reducing oxidative stress and cytokine production. They reduce the deposition of abnormal proteins by crossing the blood-brain barrier. The purpose of this article is to discuss the role of insulin dysfunction in the pathogenesis of neurological diseases, specifically dementia. Additionally, we reviewed the therapeutic target (GLP-1) and its receptor activators as a possible treatment of dementia.

Echinocystic Acid Inhibits Inflammation and Exerts Neuroprotective Effects in MPTP-Induced Parkinson’s Disease Model Mice

Parkinson’s disease (PD), the second primary neurodegenerative disease affecting human health, is mainly characterized by dopaminergic neuron damage in the midbrain and the clinical manifestation of movement disorders. Studies have shown that neuroinflammation plays an important role in the progression of PD. Excessively activated microglia produce several pro-inflammatory mediators, leading to damage to the surrounding neurons and finally inducing neurodegeneration. Echinocystic acid (EA) exhibits an anti-inflammatory effect in peripheral tissues. However, whether it inhibited neuroinflammation remains unclear. Therefore, the current study investigates the effect of EA on neuroinflammation and whether it can improve PD symptoms through inhibiting neuroinflammation. In our experiments, we discovered that EA inhibited the production of pro-inflammatory mediators in LPS-exposed BV2 cells. Further mechanism-related studies revealed that EA inhibited inflammation by activating PI3K/Akt and inhibiting NF-κB and MAPK signal pathways in LPS-induced BV2 cells. Research revealed that EA eases microglia-mediated neuron death in SN4741 and SHSY5Y cells. In in vivo studies, the results demonstrated that EA improves weight loss and behavioral impairment in MPTP-induced mice. Further studies have revealed that EA inhibited dopaminergic neuron damage and inflammation in the mice midbrain. In conclusion, our study demonstrated that EA inhibits neuroinflammation and exerts neuroprotective effects by activating PI3K/Akt and inhibiting NF-κB and MAPK signal pathways in vivo and in vitro.

Implication of Adult Hippocampal Neurogenesis in Alzheimer’s Disease and Potential Therapeutic Approaches

Alzheimer’s disease is the most common neurodegenerative disease, affecting more than 6 million US citizens and representing the most prevalent cause for dementia. Neurogenesis has been repeatedly reported to be impaired in AD mouse models, but the reason for this impairment remains unclear. Several key factors play a crucial role in AD including Aβ accumulation, intracellular neurofibrillary tangles accumulation, and neuronal loss (specifically in the dentate gyrus of the hippocampus). Neurofibrillary tangles have been long associated with the neuronal loss in the dentate gyrus. Of note, Aβ accumulation plays an important role in the impairment of neurogenesis, but recent studies started to shed a light on the role of APP gene expression on the neurogenesis process. In this review, we will discuss the recent approaches to neurogenesis in Alzheimer disease and update the development of therapeutic methods.

Can SARS-CoV-2 Infection Exacerbate Alzheimer's Disease? An Overview of Shared Risk Factors and Pathogenetic Mechanisms

The current coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus (SARS-CoV)-2, is affecting every aspect of global society, including public healthcare systems, medical care access, and the economy. Although the respiratory tract is primarily affected by SARS-CoV-2, emerging evidence suggests that the virus may also reach the central nervous system (CNS), leading to several neurological issues. In particular, people with a diagnosis of Alzheimer's disease (AD) are a vulnerable group at high risk of contracting COVID-19, and develop more severe forms and worse outcomes, including death. Therefore, understanding shared links between COVID-19 and AD could aid the development of therapeutic strategies against both. Herein, we reviewed common risk factors and potential pathogenetic mechanisms that might contribute to the acceleration of neurodegenerative processes in AD patients infected by SARS-CoV-2.

The role of melatonin in the treatment of type 2 diabetes mellitus and Alzheimer's disease

In type 2 diabetes mellitus (T2DM) and its related disorders like obesity, the abnormal protein processing, oxidative stress and proinflammatory cytokines will drive the activation of inflammatory pathways, leading to low-grade chronic inflammation and insulin resistance (IR) in the periphery and impaired neuronal insulin signaling in the brain. Studies have shown that such inflammation and impaired insulin signaling contribute to the development of Alzheimer's disease (AD). Therefore, new therapeutic strategies are needed for the treatment of T2DM and T2DM-linked AD. Melatonin is primarily known for its circadian role which conveys message of darkness and induces night-state physiological functions. Besides rhythm-related effects, melatonin has anti-inflammatory and antioxidant properties. Melatonin levels are downregulated in metabolic disorders with IR, and activation of melatonin signaling delays disease progression. The aim of this Review is to highlight the therapeutic potentials of melatonin in preventing the acceleration of AD in T2DM individuals through its therapeutic mechanisms, including antioxidative effects, anti-inflammatory effects, restoring mitochondrial function and insulin sensitivity.

Precise gene delivery systems with detachable albumin shell remodeling dysfunctional microglia by TREM2 for treatment of Alzheimer's disease

Intervention of the over-activated microglia-aggravated neuroinflammation represents a promising therapeutic strategy for Alzheimer's disease (AD). Upregulation of triggering receptor expressed on myeloid cells-2 (TREM2) attenuates the neuroinflammatory processes and normalizes the dysfunctional microglia. However, Trem2-gene therapy for AD by the effective non-invasive delivery systems is unexploited. Herein, we report the microglia-targeted gene delivery systems (PHSA@PF/pTREM2) composed of a core of fluorinated polyethylenimine condensing the TREM2-encoding plasmid (PF/pTREM2) and a shell of human serum albumin conjugated with both cis-aconitic anhydride and neural cell adhesion molecule-mimetic peptide P2 (PHSA). Thanks to the shedding effect of the albumin coated, PHSA@PF/pTREM2 exhibit prolonged blood circulation and low cytotoxicity. PHSA@PF/pTREM2 achieve brain accumulation as high as 2.17% injected dose per gram of brain and the microglial-targeting effect (targeting specificity of 41.9%) via the systemic administration. The nanocomplexes can be detached PHSA-shell in the acidic endo-lysosomes via the cleavage of cis-aconitic amide bond, resulting in PF/pTREM2 exposure for efficient endo-lysosomal escape and gene transfection. PHSA@PF/pTREM2 upregulate the TREM2 level and regulate microglial polarization toward M2-phenotype for remodeling the inflammatory microenvironment and enhanced Aβ clearance, leading to an improvement of cognitive performance in APP/PS1 mice. This work provides a promising gene delivery platform to reverse dysfunctional microglia for AD therapy.

Structural analysis of the microglia-interneuron interactions in the CA1 hippocampal area of the APP/PS1 mouse model of Alzheimer's disease

Microglia can interact with glutamatergic neurons and, through control of synaptic elements, regulate their physiological function. Much less is known about the partnership between microglia and GABAergic inhibitory interneurons. Here, we compared the interactions between microglia and parvalbumin (PV+) and somatostatin (SOM+) expressing interneurons in the CA1 hippocampal area of APP/PS1 transgenic mice that mimic certain aspects of the Alzheimer's disease (AD). We first uncovered a high level of interactions between microglia and two types of interneurons, with 98% of SOM+ and 90% of PV+ cells receiving different types of putative microglial contacts. The latter included the microglia soma to the interneuron soma (Soma_MG -to-Soma_IN ), the microglia process to the interneuron soma (Process_MG -to-Soma_IN ) and the microglia process to the interneuron dendrite (Process_MG -to-Dend_IN ) interactions. Moreover, we found significantly larger areas of interaction for the Soma_MG -to-Soma_IN and the Process_MG -to-Dend_IN type of contacts between microglia and SOM+ cells. In contrast, PV+ cells exhibited larger areas for the Process_MG -to-Soma_IN interactions. Second, in APP/PS1 mice, although the overall microglia interactions with interneurons remained preserved, the fraction of interneurons receiving putative microglia contacts on their dendrites was reduced, and larger areas of interactions were observed for somatic contacts, suggesting a stronger modulation of the interneuron output by microglia in AD. In summary, these results reveal microglia as important partners of hippocampal PV+ and SOM+ GABAergic cells, with interneuron type-specific pattern of interactions. Thus, microglia may play an essential role in the operation of interneurons under normal conditions and their dysfunction in disease.

Rhynchophylline Administration Ameliorates Amyloid-β Pathology and Inflammation in an Alzheimer's Disease Transgenic Mouse Model

Alzheimer's disease (AD), the most common neurodegenerative disease, has limited treatment options. As such, extensive studies have been conducted to identify novel therapeutic approaches. We previously reported that rhynchophylline (Rhy), a small molecule EphA4 inhibitor, rescues impaired hippocampal synaptic plasticity and cognitive dysfunctions in APP/PS1 mice, an AD transgenic mouse model. To assess whether Rhy can be developed as an alternative treatment for AD, it is important to examine its pharmacokinetics and effects on other disease-associated pathologies. Here, we show that Rhy ameliorates amyloid plaque burden and reduces inflammation in APP/PS1 mice. Transcriptome analysis revealed that Rhy regulates various molecular pathways in APP/PS1 mouse brains associated with amyloid metabolism and inflammation, specifically the ubiquitin proteasome system, angiogenesis, and microglial functional states. These results show that Rhy, which is blood-brain barrier permeable, is beneficial to amyloid pathology and regulates multiple molecular pathways.

Ultrasound-Responsive Systems as Components for Smart Materials

Smart materials can respond to stimuli and adapt their responses based on external cues from their environments. Such behavior requires a way to transport energy efficiently and then convert it for use in applications such as actuation, sensing, or signaling. Ultrasound can carry energy safely and with low losses through complex and opaque media. It can be localized to small regions of space and couple to systems over a wide range of time scales. However, the same characteristics that allow ultrasound to propagate efficiently through materials make it difficult to convert acoustic energy into other useful forms. Recent work across diverse fields has begun to address this challenge, demonstrating ultrasonic effects that provide control over physical and chemical systems with surprisingly high specificity. Here, we review recent progress in ultrasound–matter interactions, focusing on effects that can be incorporated as components in smart materials. These techniques build on fundamental phenomena such as cavitation, microstreaming, scattering, and acoustic radiation forces to enable capabilities such as actuation, sensing, payload delivery, and the initiation of chemical or biological processes. The diversity of emerging techniques holds great promise for a wide range of smart capabilities supported by ultrasound and poses interesting questions for further investigations.

Ginkgolide B inhibits NLRP3 inflammasome activation and promotes microglial M2 polarization in Aβ1-42-induced microglia cells

Nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome-mediated chronic neuroinflammation plays a crucial role in the progression of Alzheimer's disease (AD), which is related to microglial activation. Using quantitative proteomic analysis, we identified 25 up-regulated and 83 down-regulated proteins in amyloid beta (Aβ)_1-42-induced BV2 cells. Among the differentiallyexpressedproteins involved in inflammation, the NLRP3 protein level increased dramatically. Ginkgolide B (GB) prevents Aβ-induced neuroinflammation and neurotoxic effects in multiple neurodegenerative disorders. However, its role in NLRP3 inflammasome-mediated neuroinflammation in AD remain unknown. We found that GB treatment ameliorated Aβ_1-42-induced pathological damages and inhibited NLRP3 inflammasome activation. Furthermore, GB enhanced the expression of M2 microglial markers and suppressed the expression of M1 microglial markers. Our findings suggest that GB treatment prevents the pathological processes of AD and suppresses neuroinflammation by inhibiting NLRP3 inflammasome activation and promoting microglial M2 polarization.

Air pollution and trajectories of adolescent conduct problems: the roles of ethnicity and racism; evidence from the DASH longitudinal study

PURPOSE

No known UK empirical research has investigated prospective associations between ambient air pollutants and conduct problems in adolescence. Ethnic minority children are disproportionately exposed to structural factors that could moderate any observed relationships. This prospective study examined whether exposure to PM2.5 and NO2 concentrations is associated with conduct problems in adolescence, and whether racism or ethnicity moderate such associations.

METHODS

Longitudinal associations between annual mean estimated PM2.5 and NO2 concentrations at the residential address and trajectories of conduct problems, and the potential influence of racism and ethnicity were examined school-based sample of 4775 participants (2002-2003 to 2005-2006) in London, using growth curve models.

RESULTS

Overall, in the fully adjusted model, exposure to lower concentrations of PM2.5 and NO2 was associated with a decrease in conduct problems during adolescence, while exposure to higher concentrations was associated with a flattened trajectory of conduct symptoms. Racism amplified the effect of PM2.5 (β = 0.05 (95% CI 0.01 to 0.10, p < 0.01)) on adolescent trajectories of conduct problems over time. At higher concentrations of PM2.5, there was a divergence of trajectories of adolescent conduct problems between ethnic minority groups, with White British and Black Caribbean adolescents experiencing an increase in conduct problems over time.

CONCLUSION

These findings suggest that the intersections between air pollution, ethnicity, and racism are important influences on the development of conduct problems in adolescence.

The Amyloid-β Pathway in Alzheimer's Disease

Breakthroughs in molecular medicine have positioned the amyloid-β (Aβ) pathway at the center of Alzheimer's disease (AD) pathophysiology. While the detailed molecular mechanisms of the pathway and the spatial-temporal dynamics leading to synaptic failure, neurodegeneration, and clinical onset are still under intense investigation, the established biochemical alterations of the Aβ cycle remain the core biological hallmark of AD and are promising targets for the development of disease-modifying therapies. Here, we systematically review and update the vast state-of-the-art literature of Aβ science with evidence from basic research studies to human genetic and multi-modal biomarker investigations, which supports a crucial role of Aβ pathway dyshomeostasis in AD pathophysiological dynamics. We discuss the evidence highlighting a differentiated interaction of distinct Aβ species with other AD-related biological mechanisms, such as tau-mediated, neuroimmune and inflammatory changes, as well as a neurochemical imbalance. Through the lens of the latest development of multimodal in vivo biomarkers of AD, this cross-disciplinary review examines the compelling hypothesis- and data-driven rationale for Aβ-targeting therapeutic strategies in development for the early treatment of AD.

The Effect of Spironolactone on β-amyloid-Induced Memory Impairment in Male Rats: The Role of Microglial Inhibition

Purpose: Neuroinflammation was indicated in the pathophysiology of Alzheimer’s disease (AD). Previous reports have also signified that spironolactone has anti-inflammatory effects. Therefore, the aim of this study was to assess the modulatory effects of spironolactone on neuroinflammation and memory loss in a rat model of AD.

Methods: The β-amyloid protein fragment 25-35 (Aβ) was injected in the dorsal hippocampus (5 μg/2.5 μL each side) of male Sprague-Dawley rats for four consecutive days to induce memory impairment. Animals have intraperitoneally received spironolactone (10, 25, or 50 mg/kg, N = 6/ group) or vehicle for 14 days. The passive inhibitory avoidance and the novel recognition tests were used for memory evaluation. Neuroinflammation was assessed by measuring the level of Iba1 protein, a marker of microglial activation, using western immunoblotting.

Results: Different doses of spironolactone showed no significant changes in latency times and discriminations ratios in passive inhibitory avoidance and novel recognition tests, respectively, as compared to vehicle. However, spironolactone-treated groups showed significantly lower Iba1 protein levels in comparison to the vehicle-treated group (P < 0.01).

Conclusion: Spironolactone had a modulatory effect on neuroinflammation through a repressive effect on microglial activation with no valuable effect on memory improvement in a rat model of AD. The findings of this study suggest that Aβ-induced memory loss may not be directly linked to microglial activation. Spironolactone may be a potential candidate to be examined in other neuroinflammatory disorders.